/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.squareup.leakcanary;

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.Application;
import android.os.Bundle;

import static android.os.Build.VERSION.SDK_INT;
import static android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH;
import static com.squareup.leakcanary.Preconditions.checkNotNull;

@TargetApi(ICE_CREAM_SANDWICH)
public final class ActivityRefWatcher {

	public static void installOnIcsPlus(Application application,
			RefWatcher refWatcher) {
		if (SDK_INT < ICE_CREAM_SANDWICH) {
			// If you need to support Android < ICS, override onDestroy() in
			// your base activity.
			return;
		}
		ActivityRefWatcher activityRefWatcher = new ActivityRefWatcher(
				application, refWatcher);
		activityRefWatcher.watchActivities();
	}

	private final Application.ActivityLifecycleCallbacks lifecycleCallbacks = new Application.ActivityLifecycleCallbacks() {
		@Override
		public void onActivityCreated(Activity activity,
				Bundle savedInstanceState) {
		}

		@Override
		public void onActivityStarted(Activity activity) {
		}

		@Override
		public void onActivityResumed(Activity activity) {
		}

		@Override
		public void onActivityPaused(Activity activity) {
		}

		@Override
		public void onActivityStopped(Activity activity) {
		}

		@Override
		public void onActivitySaveInstanceState(Activity activity,
				Bundle outState) {
		}

		@Override
		public void onActivityDestroyed(Activity activity) {
			ActivityRefWatcher.this.onActivityDestroyed(activity);
		}
	};

	private final Application application;
	private final RefWatcher refWatcher;

	/**
	 * Constructs an {@link ActivityRefWatcher} that will make sure the
	 * activities are not leaking after they have been destroyed.
	 */
	public ActivityRefWatcher(Application application,
			final RefWatcher refWatcher) {
		this.application = checkNotNull(application, "application");
		this.refWatcher = checkNotNull(refWatcher, "refWatcher");
	}

	void onActivityDestroyed(Activity activity) {
		refWatcher.watch(activity);
	}

	public void watchActivities() {
		// Make sure you don't get installed twice.
		stopWatchingActivities();
		application.registerActivityLifecycleCallbacks(lifecycleCallbacks);
	}

	public void stopWatchingActivities() {
		application.unregisterActivityLifecycleCallbacks(lifecycleCallbacks);
	}
}
